Elevated asymmetric dimethylarginine (ADMA) levels have been observed in various conditions, including hypertension, dyslipidemia, hyperglycemia, hyperhomocysteinemia, and renal failure, and are believed to be one cause of endothelial dysfunction in these conditions. Elevated plasma ADMA concentrations are also associated with an increased risk of cardiovascular disease. As an endogenous inhibitor of nitric oxide synthase, ADMA reduces nitric oxide (NO) production. NO plays a vital part in the vascular homeostasis. Aside from being the most potent vasodilator, NO inhibits platelet aggregation, smooth muscle proliferation, and adhesion molecule expression, which all play a part in atherogenesis. Throughout the last few years, basic scientific investigation has revealed the mechanism whereby ADMA becomes elevated in patients with hypertension, hyperhomocysteinemia, hyperglycemia, hypercholesterolemia, and tobacco exposure.
Nevertheless, the field of ADMA is progressing slowly, mostly because of the laborious procedures required to quantify the molecule. A conclusive demonstration of ADMA's clinical relevance requires clinical studies with a great patient population. High pressure liquid chromatography (HPLC) is the most commonly used method to quantify ADMA. However, the use of HPLC to quantitate ADMA suffers from several drawbacks. The most critical among them are efficiency and sensitivity. The labor-intensive extraction and derivatization steps necessary for HPLC detection not only makes the procedure more vulnerable to human errors, but also makes it unfitting for studies with a large sample size. Moreover, because the detection limit for UV detectors seldom goes below the sub-micromolar level, intracellular ADMA level in disease states remains largely unexplored, despite the fact that ADMA is generated intracellularly.
There is a need in the art for methods of detecting and quantitating ADMA that are simple, efficient, and readily adapted to high-throughput analysis. The present invention addresses this need.
Literature
Takahashi (1968) J. Biol. Chem. 243:6171-6179; Stühlinger et al. (2002) J. Am. Med. Assoc. 287:1420-1426; U.S. Pat. No. 6,358,699; Teerlink et al. (2002) Anal. Biochem. 303:131-137; Dobashi et al. (2002) Analyst 127:54-59; Vishwanathan et al. (2000) J. Chromatogr. B. Biomed. Sci. Appl. 748:157-166; Pi et al. (2000) J. Chromatogr. B. Biomed. Sci. Appl. 742:199-203; Chen et al. (1997) J. Chromatogr. B. Biomed. Sci. Appl. 692:467-471; Pettersson et al. (1997) J. Chromatogr. B. Biomed. Sci. Appl. 692:257-262.